The present invention relates to a location information detecting method and system by which location information is detected by means of communications between a radio IC tag and an interrogator unit.
There is a known system for establishing communications between a radio IC tag and an interrogator unit by using radio frequencies, in for example, the short wavelength region or the ultra short wavelength region, in which a radio IC tag (RFID) is attached to the surface of an article, and an interrogator unit is used to read information stored in the radio IC tag by moving the article close to the interrogator unit. (See Japanese Patent Laid-Open (Kokai) Publication No. 2001-357363). By determining whether an article has passed by the interrogator unit or not, this type of system can manage the distribution and inventory status of goods based on the information read by the interrogator unit.
Moreover, by attaching the radio IC tag to an identification card (such as an access permit) carried by a person and having the interrogator unit read the information stored in the radio IC tag when the person enters or leaves a specified place, it is possible to apply the system to the management of the person's access status and to the detection of the person's movements.
In the system of Japanese Patent Laid-Open (Kokai) Publication No. 2001-357363 (p.p. 2–3 and FIG. 1), the radio IC tag is attached to the article and the interrogator unit is fixed at a specified location. Therefore, even if the interrogator unit reads the information stored in the radio IC tag, it is impossible to detect information relating to the location of the radio IC tag.
It would be a significant advance in the art to detect the information relating to the location of the radio IC tag, using the interrogator unit.